In recent years, as larger amount of information is transmitted at higher speed with larger transmission capacity over telecommunications networks, optical communication technologies have been increasingly employed to meet the needs. In the optical communication, an electrical signal is converted into an optical signal which is transmitted over an optical fiber and, at the receiving end, the optical signal is converted back to the electrical signal. Conversion between the electrical signal and the optical signal is carried out by an optical device such as semiconductor laser or photo diode, while a fiber optic receptacle is used to establish the coupling between the optical device and the optical fiber.
For the fiber optic receptacle, various typos are used depending on the application, such as one that has a fiber stub which holds the optical fiber, or one that employs a hollow stopper, while optical communication modules operating at relatively low transmission speeds in a range from 155 Mbps to 1 Gbps employ fiber optic receptacle that uses a hollow stopper. For example, Japanese Unexamined Patent Publication (Kokai) No. 2005-99748 discloses fiber optic receptacle having a fiber stub inserted into the bore of a sleeve and is fixed therein with an adhesive. In the fiber optic receptacle disclosed in this publication, a ferrule provided on the side of an optical connector is inserted into the bore of the sleeve and is put into contact with one end of the fiber stub.
Japanese Unexamined Patent Publication (Kokai) No. 2004-287198 and Japanese Unexamined Patent Publication (Kokai) No. 6-40903 disclose fiber optic receptacles for low-speed optical modules. FIG. 6 shows a fiber optic receptacle having the structure disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2004-287198, where a ferrule 15 of the optical connector makes contact with a stopper surface 17. Japanese Unexamined Patent Publication (Kokai) No. 6-40903 discloses such a structure as a stopper which makes contact with the distal end of a ferrule is made of ceramics.
The fiber optic receptacle disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2005-99748 has such a problem that, since the fiber stub is inserted into the bore of the sleeve and is fixed therein with an adhesive, the adhesive must be applied evenly so as to prevent the fiber stub from being eccentrically located, thus making an obstacle to the reduction of manufacturing cost.
The fiber optic receptacle disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2004-287198 has such problems that, since the stopper surface 17 which makes contact with the ferrule 15 of the optical connector is made of a metal, there are problems of durability of the ferrule 15 against repetitive impact and difficulty in inserting the ferrule 15 due to deposition of dirt formed from wearing of the stopper surface 17 onto the inner circumference 19 of the sleeve 1. In the case of the sleeve of a receptacle used in single mode operation, in particular, where the clearance between the inner circumference of the sleeve and the outer circumference of the formula of the optical connector is about 1 to 2 μm, even a small amount of wear dust deposited on the inner circumference may make it impossible to insert or pull out the ferrule of the optical connector.
Furthermore, ill the fiber optic receptacle disclosed in Japanese Unexamined Utility Model Publication (Kokai) No. 6-40903 where the stopper is made of ceramics, there is a problem that the manufacturing cost cannot be reduced as the number of component parts increases or it is necessary to polish the inner circumference of the sleeve and/or control the accuracy after assembling the sleeve.
Accordingly, an object of the present invention is to provide a fiber optic receptacle which can be assembled with high precision, has high reliability and is low-priced.